Factors Influencing Cities’ Publishing Efficiency

In the past decades, the publication output of China has radically increased, and the growth rate has exceeded that of any other countries in the world. Furthermore, the publication outputs of some emerging countries, such as South Korea, Taiwan, India, and Iran, have also significantly increased (Csomós 2018; Grossetti et al. 2014; Maisonobe et al. 2017). Naturally, the annual outputs of the United States, Canada, the Western European countries, and Japan have also increased, but they have witnessed a much smaller growth rate than the emerging countries. Therefore, the share of the most developed countries in the production of science has been decreasing for decades (Leydesdorff and Wagner 2009).

Some cities in the world have long been considered as an outstanding locus of the production of science (Matthiessen and Schwarz 1999; Van Noorden 2010), and the growth rate of these cities’ publication output is much higher than that of the countries in which they are located. By the beginning of the 2010s, the annual publication output of Beijing surpassed that of any other city in the world (Table 1). In the period from 2014 to 2016, it produced a greater number of scientific publications than Japan. Furthermore, Seoul, Tehran, and São Paulo have also experienced a significant increase in their publication output, and due to this development, their position in the ranking has approached that of Tokyo, Paris, New York, and Boston.

Table 1

Top 50 cities producing the greatest number of articles between 2014 and 2016.

However, many researchers wonder about the quality of publications produced in Brazilian, Chinese, Indian, Iranian, and even South Korean cities, which is also reflected in their low citation impact (Andersson et al. 2014; Maisonobe et al. 2017; Xie et al. 2014; Van Noorden 2010; Zhou et al. 2009a). In the period from 2014 to 2016, the greatest number of highly cited articles were produced in Beijing (see Table 2), which is not surprising, if we consider the extremely high total publication

Table 2

Top 50 cities producing the greatest number of highly cities articles between 2014 and 2016.

output of Beijing in terms of the number of articles. Table 2 shows that the difference between the output of Beijing and Boston in terms of the number of highly cited articles is very small, while the total output of Beijing is three times greater than that of Boston (see Table 1). Comparing the rankings in Tables 1 and 2, the positions of some top-ranked cities in terms of total output (e.g., Tokyo and Seoul) have dropped in the ranking of cities producing the greatest number of highly cited articles. In addition, such emerging cities, such as Tehran and São Paulo, which both produced a substantial number of articles between 2014 and 2016, have disappeared from the ranking of the top 50 cities with the greatest number of highly cited articles.

A different geographical pattern will emerge if we focus on measuring cities’ publishing efficiency (Figure 1). The mean publishing efficiency of the 554 cities included in the analysis is 1.818, which means that an average of 1.818% of all articles published in these cities in the period from 2014 to 2016 received enough citations to belong to the top 1% of highly cited articles. However, there are significant geographic differences behind the mean value. Figure 1 shows that the publishing efficiency of most Chinese, Japanese, and South Korean cities (many of which have high publication output in terms of the number of articles) is quite low, while the publishing efficiency of most Northern American and Western European cities is considerably higher. This information is not novel since, directly or indirectly, it has also been described by Van Noorden (2010), Bornmann and Waltman (2011), and Leydesdorff et al. (2014).

Figure 1

However, a more fundamental question is whether there are factors influencing cities’ publishing efficiency. Are there any general factors producing high publishing efficiency? Can we find general factors characterising cities having low publishing efficiency? Why is the publishing efficiency of Villejuif (France), Menlo Park, California (United States), or Jeddah (Saudi Arabia) high, and what are the reasons behind the low publishing efficiency of Tehran (Iran), Shenyang (China), and Niigata (Japan)? To answer these questions, we should explore and compare the general factors characterising the most efficient and least efficient cities.

The mean publishing efficiency of the top 100 most efficient cities is 3.179, while that of the bottom 100 least efficient cities is 0.621. In the top 100 cities, in the period from 2014 to 2016, a mean of 13,830 articles per city was produced, of which a mean of 444.71 articles per city received enough citations to belong to the top 1% of highly cited articles. In the same period, in the bottom 100 cities, a mean of 8,885 articles per city was produced, of which only a mean of 60.44 articles per city received enough citations to belong to the top 1% of highly cited articles. That is, the total output in terms of the number of articles of the top 100 most efficient cities is only 1.5 times greater than that of the bottom 100 least efficient cities. In contrast to the results above, there is a difference of more than 7.4 times between the number of highly cited articles produced in the top 100 cities and those produced in the bottom 100 cities. When exploring the general factors influencing cities’ publishing efficiency, I will focus on presenting the differences between the top 100 most efficient cities and the bottom 100 least efficient cities.

The general factors examined in this paper are as follows: the linguistic environment of cities, cities’ economic development level (both derived from country-level data), the location of excellent organisations, cities’ international collaboration patterns, and their scientific field profile. The full list of the top 100 most efficient cities is available in Appendix 1, and the list of the bottom 100 least efficient cities is in Appendix 2.

It is a generally accepted fact that English has acquired an almost exclusive status as the international language of scientific communication (i.e., the neutral “lingua franca”), leaving little space for other languages in science (Björkman 2011; López-Navarro et al. 2015; Tardy 2004; van Weijen 2012). Although the most important indexing and abstracting databases (i.e., the Web of Science and Scopus) have been including an increasing number of non-English language journals, English language journals are still significantly overrepresented (Li et al. 2014; Mongeon and Paul-Hus 2016). According to Paasi (2005), ‘Anglo-American journals dominate the publishing space in science’, and the international journal publication space is ‘particularly limited to the English-speaking countries’. Furthermore, as Braun and Dióspatonyi (2005), Braun et al. (2007), and Leydesdorff and Wagner (2009) asserted in terms of gatekeepers like editors-in-chief and editorial board member positions, the dominance of the United States is still unchallenged. Considering the above facts, the English language is assumed to be one of the main factors that influence cities’ publishing efficiency.

Figure 3

In this paper, I classified cities according to the Anglosphere system introduced by Bennet (2007). In this system, the United States, the United Kingdom, Canada, Australia, New Zealand, and Ireland belong to the Anglosphere−Core. Countries in the Anglosphere−Middle sphere (e.g., Nigeria and South Africa) have several official languages, including English (which is the principal language of administration and commerce), but ‘where the primary connections to the outside world are in English’. The Anglosphere−Outer sphere consists of English-using states of other civilisations, including India, Pakistan, Bangladesh, the Arab states formerly under British control (primarily in the Middle East), and the Islamic former colonies of Britain (e.g., Malaysia and African states).

A total of 230 cities (out of 554 cities included in the analysis) are in countries in the Anglosphere, from which 195 cities are in countries in the Anglosphere−Core. Countries outside the Anglosphere are home to 324 cities. The mean publishing efficiency of cities in countries in the Anglosphere is 2.271, while that of the rest of the cities is 1.497. That is, the mean publishing efficiency of cities in countries in the Anglosphere is greater than that of the rest of the cities by 50%. If we focus on the mean publishing efficiency of cities located in countries in the Anglosphere− Core, it increases to 2.439.

As for the top 100 most efficient cities, 73% of them are in countries in the Anglosphere, and 70% of them can be found in countries in the Anglosphere–Core. The mean publishing efficiency of cities belonging to the latter group is 3.235. In contrast, 85% of the bottom 100 least efficient cities are in countries outside the Anglosphere, and 99% of them are in countries outside the Anglosphere−Core. Loughborough (England), having a publishing efficiency of 0.868, is the only city in the group of the bottom 100 cities that can be found in the Anglosphere–Core.

In conclusion, the publishing efficiency of cities located in countries in the Anglosphere (especially in the Anglosphere−Core) is much higher than that of any other cities located in countries outside the Anglosphere. That is, English is not only the international language of scientific communication but also the most fundamental factor influencing cities’ publishing efficiency.

Some researchers have observed linear or exponential correlation between scientometric indicators (e.g., the number of publications) and economic development indicators (e.g., GDP per capita or income per capita) (de Solla Price 1978; Kealey 1996; King 2004), while others assert that the correlation between these different sets of indicators is far from clear (Lee at al. 2011; Meo et al. 2013; Vinkler 2008; Vinkler 2010). It is, however, more commonly accepted that the higher the GDP per capita or the income level of a country is, the more likely it is that a greater number of publications will be produced in that country. The question is whether there is a relationship between cities’ publishing efficiency (as a scientometric indicator) and cities’ per capita income level (derived from country-level data).

The classification of countries (and cities) by income level is based upon data obtained from the World Bank Country and Lending Groups database

World Bank Country and Lending Groups https://datahelpdesk.worldbank.org/knowledgebase/articles/906519-world-bank-country-and-lending-groups

Results show that 434 out of 554 cities included in the analysis are in high-income countries, 93 of them are in upper middle-income countries, and only 27 cities can be found in lower middle-income countries. None of the cities are in low-income countries. That is, most cities producing high publication output in terms of the number of articles (i.e., at least 3,000 articles in the period from 2014 to 2016) are in high-income countries. The mean publishing efficiency of cities from high-income countries is 2.057, that of cities located in upper middle-income countries is 0.997, and the mean publishing efficiency of cities from lower middle-income countries is only 0.881. There is a difference of more than double between the mean publishing efficiency of cities located in high-income countries and that of cities located in upper middle-income countries. The difference between the mean publishing efficiency of cities in upper middle-income countries and that of cities in lower middle-income countries seems to be insignificant.

As for the top 100 most efficient cities, 98% of them are in high-income countries, and only 2% of them can be found in upper middle-income countries. As compared to the quasi-homogeneous group of the top 100 cities, the bottom 100 least efficient cities show a more complex picture; 18% of them are in lower middle-income countries, 46% of them are in upper middle-income countries, but 36% of the bottom 100 least efficient cities are in high-income countries. Based on former studies available in the literature, this latter result might not have been expected; therefore, it requires more explanation.

As was mentioned above, most of the top 100 cities were in Northern America (primarily in the United States) and Europe (primarily in Northern European and Western European countries). Almost all countries in these regions are high-income countries. Contrary to the most efficient cities, none of the least efficient cities are in Northern America. Furthermore, only 17% of the bottom 100 cities are in European countries; except for five cities, all of them are in Eastern European countries (including Russia). Results show that 11 out of the 17 least efficient European cities are in high-income countries, and six of them are in Poland. Figure 4 illustrates that many cities producing low publishing efficiency are in Eastern Asian high-income countries. Half of these cities are in South Korea (11 cities), and another half are in Japan (12 cities); i.e., in countries that belong to the most developed countries in the world in terms of income level. One might suggest that if South Korea and Japan are high-income countries, cities located in South Korea and Japan should produce high publishing efficiency. One reason for this discrepancy may be that both Korean and Japanese languages are considered language isolates (Campbell, 2010), and it is well studied how problematic it is for Japanese people to acquire sufficient communicative skills in English (even if they are researchers) (see, for example, Butler and Iino, 2005, Iwai, 2008). In contrast, for example, one survey shows that the Dutch have the world’s best non-native English skills (see, EF EPI English Proficiency Index, https://www.ef.co.hu/epi/) Therefore, it is not surprising that the collaboration intensity of both Japan and South Korea with the United States is lower (the proportion of co-authored papers indexed in the WoS during 2014–2016 was 10.6 and 13.8 percent for these countries, respectively) than that of European high-income countries, such as Germany and the Netherlands (the proportion of co-authored papers indexed in the WoS during 2014–2016 was 15.9 and 18.0 percent for these countries, respectively). It has however been determined that the higher the intensity of the collaboration between a country and the United States is, the more likely it is that co-authored papers will receive a higher number of citations (Pan et al., 2012; Sud and Thelwall, 2016), and have a greater chance to become highly cited papers.

Figure 4

Loughborough (England) is the only city in the bottom 100 least efficient cities that is in a high-income country belonging to the Anglosphere−Core. Beer-Sheva (Israel), a city in the group of the bottom 100 least efficient cities, is also in a high-income country, but is in the Anglosphere−Outer sphere. In fact, many of the bottom 100 cities are in countries in the Anglosphere−Outer sphere, but all of them are in lower middle-income countries, primarily in Southeast Asia (11 cities are in India, and one is in Pakistan).

East Asia is home to 46% of the bottom 100 least efficient cities. Beside Japan and South Korea, most of these cities are in China. While none of the East Asian countries included in the analysis belong to the group of the low-income or lower middle-income countries (Japan and South Korea are high-income countries, and China is an upper middle-income country), the publishing efficiency of the East Asian cities is rather low. Kawaguchi (Japan), the city producing the highest publishing efficiency in the region, is ranked only 138^th. The facts above suggest that the economic development level of the cities is a key factor influencing publishing efficiency, which is reinforced by the fact that almost all cities in the group of the top 100 cities are in high-income countries, but it is not the most important factor.

The examination of factors like the dominance of the English language and cities’ economic development level will bring us closer to understanding why cities’ publishing efficiency differs from each other; however, we need deeper insight to obtain a precise picture of publishing efficiency. For example, country-level data allows us to understand why the publishing efficiency of Canadian and Chinese cities significantly differ from each other but does not help us to understand why the publishing efficiency of Kawaguchi is higher or why that of Niigata is lower than the mean publishing efficiency of Japanese cities. To examine cities’ publishing efficiency in a more precise way, we need to focus on some general as well as more city-specific factors, like the location of excellent organisations, cities’ international collaboration patterns, and the productivity of specific research areas.

For example, in Kawaguchi, most publications were produced by the Japan Science and Technology Agency, one of Japan’s excellent scientific organisations; therefore, the publishing efficiency of Kawaguchi is considerably higher than that of other Japanese cities. That is, which cities in the world are home to excellent organisations (e.g., universities and governmental and international research institutions) should be examined. The question is whether these organisations are exclusively located in cities producing high publishing efficiency or whether some of them might be found in cities with low publishing efficiency.

In the paper by Van Noorden (2010: 907) an important question arose: What is the reason Boston ranks top in several analyses of scientific quality? A brief answer was given by José Lobo, a statistician and economist who was affiliated with Arizona State University at Tempe: ‘Take three or four of the best universities in the world, put them in a city with a seaport, and voilà!’ Naturally, the question requires a more complex answer (as was later also explained by Van Noorden), but it calls attention to a key factor: the scientific performance of cities significantly depends on whether they are home to top-ranked universities.

Although many research institutions, hospitals, governmental organisations (e.g., ministries and departments), NGOs, and companies have a significant publication output (see, for example, Archambault and Larivière 2011; Csomós and Tóth 2016; Hicks 1995), scientific publications are primarily produced by universities all over the world. In recent years, university rankings have gained in popularity. The main goal of ranking and comparing universities in terms of scientific output (of which the publication output is a vital component) is to make the most prestigious universities visible worldwide. There are several different world university rankings available (e.g., CWTS Leiden Ranking, The Times Higher Education World University Rankings, QS World University Rankings, and Academic Ranking of World Universities – ARWU), which are all based upon different input data. However, each ranking attributes more or less significance to bibliometric indicators, such as the number of publications produced in a given university, the quality (citation impact) of scientific publications, or the number of articles published in top journals (see, for example, Docampo et al. 2015; Frenken et al. 2017; Piro and Sivertsen 2016; Shehatta and Mahmood 2016). Naturally, the methodologies of how university rankings are produced differ from each other; thus, university rankings are different in terms of top university rankings (Abramo and D’Angelo 2015; Lin et al. 2013).

From the point of view of this analysis, university rankings contain indicative information only. I chose to use the Academic Ranking of World Universities (ARWU) published annually by the Shanghai Ranking Consultancy because the importance of the Shanghai ranking has become recognized by both governments and universities; further, according to Docampo and Cram (2014), the ‘ranking has become a major resource for exploring the characteristics and quality of academic institutions and university systems worldwide.’ I examined whether there is a relationship between the location of top-ranked universities and cities’ publishing efficiency. Top-ranked universities correspond to universities having been ranked among the top 100 universities on one of the ARWU lists of 2014, 2015, and 2016.

In the period from 2014 to 2016, the top 100 universities were in 95 cities, some of which were home to more than one top-ranked university (e.g., New York, London, Boston, Pittsburgh, Munich, Stockholm, and Zurich). The publishing efficiency of cities that were home to the top 100 universities averages 2.641, while that of the rest of the cities averages 1.648. That is, the mean publishing efficiency of cities that are home to the top 100 universities is higher than that of the rest of the cities by 60%. These results suggest that the location of top-ranked universities significantly influences cities’ publishing efficiency. In other words, it seems to be a logical assumption that top-ranked universities are primarily located in the most efficient cities. Thus, we should examine which of the top 100 most efficient cities are home to top-ranked universities.

Figure 5 shows that it is not an exclusive privilege of the most efficient cities to be home to top-ranked universities. Only 43% of the top 100 universities are in the top 100 most efficient cities. Furthermore, there are many cities worldwide (including Chinese and Japanese cities), that do not belong to the top 100 most efficient cities; yet, they are home to top-ranked universities. In the group of the bottom 100 cities, Moscow (Russia) is the only city that is home to a top-ranked university.

Figure 5

The location of top-ranked universities is considered an important but not decisive factor influencing cities’ publishing efficiency. Examining the ranking of the most efficient cities, there are two cities (Villejuif, France and Menlo Park, California, USA) topping the ranking that are not home to top-ranked universities as ranked by the ARWU.

It should be noted that ARWU is just one of the alternatives to rank universities. Naturally, other organisations produce different rankings with different universities in top positions. For example, out of the top 10 universities, only Harvard University and Stanford University appear in both the CWTS Leiden Ranking of 2017 and the ARWU list of 2017. Contrary to this example, the groups of the top 10 universities in the QS World University Rankings of 2017 and the ARWU list differ from each other by only three universities. In addition, there are many top-ranked universities that are not included in the group of top 100 universities on the ARWU list but are in cities with high publishing efficiency. For example, Rotterdam, the forty-second most efficient city in the world, is home to the Erasmus University Rotterdam, which ranked 101-150 (i.e., outside but close to the top 100 universities).

The question arises as to what kind of organisations (but not universities) are in cities like Villejuif, Menlo Park, California, Upton, New York (United States), Greenbelt, Maryland (United States), Didcot (England), etc., which produce very high publishing efficiency. The explanations are as follows.

Villejuif, the city with the highest publishing efficiency in the world, is home to the ‘Institut Gustave Roussy’, one of the world’s leading cancer-research institutions and the premier oncology centre and teaching hospital in Europe. Although Villejuif is a city (commune) having 50 thousand inhabitants, it is a suburb of Paris, about seven kilometres from its centre.

Menlo Park is home to the SLAC National Accelerator Laboratory, a linear accelerator that is owned by the US Department of Energy and operated by the Stanford University. Currently, SLAC is the world’s largest linear accelerator and is one of top research centres for accelerator physics. The city of Menlo Park, with a population of 32 thousand, is in the San Francisco Bay Area between San Francisco and San Jose (i.e., in one of the fastest growing regions in the world that is home to many innovative companies and top-ranked universities). Additionally, Didcot has 25 thousand inhabitants and is 16 km south of Oxford. Didcot is home to the Rutherford Appleton Laboratory, a world-renowned research centre for particle physics and space science.

Cities such as Villejuif, Menlo Park, and Didcot can be characterised the same way; they are smaller cities, towns, or villages located in metropolitan areas and are home to quasi-independent research institutions (e.g., national laboratories) generally operating under the umbrella of prestigious universities. Naturally, top research institutions are in large cities as well, but being surrounded by universities, their visibility in terms of publication output is much lower, even if they produce very high publishing efficiency. For example, the total publication output of Geneva (Switzerland) is produced by many organisations, including the European Organisation for Nuclear Research (CERN), the World Health Organization (WHO), and the University of Geneva. In the period from 2014 to 2016, almost 60% of Geneva’s total publication output came from the University of Geneva, which has been ranked among the top 100 universities on the ARWU list, and which publishing efficiency is as high as 3.33. However, if we compare the publishing efficiency of the University of Geneva to that of the CERN (5.37) and the WHO (6.86), it seems rather low. The same pattern appears in large cities like New York, London, Paris, Los Angeles, and Tokyo.

In conclusion, a positive relationship can be detected between the location of top-ranked universities and cities’ high publishing efficiency. However, it should be noted that publications, primarily in large cities, come from different types of organisations, many of which have lower publishing efficiency than universities. Thus, some cities that are home to top-ranked universities have not been included in the top 100 most efficient cities. Furthermore, there are several top-ranked cities that are not home to top-ranked universities (or any universities); yet, they produce a very high publishing efficiency.

In recent years, the number of publications produced by single authors has been decreasing, while the number of co-authored publications and number of co-authors in publications have been increasing rapidly (Abramo et al. 2017; Castelvecchi 2015; Uddin et al. 2012). Therefore, cities’ international collaboration patterns have become more complex (i.e., authors affiliated with a given city have been collaborating with a growing number of co-authors affiliated with other cities in other countries). Naturally, cities’ international collaboration patterns are influenced by many factors, including differences between the productivity of scientific disciplines (Larivière et al. 2006; Paul-Hus et al. 2017; Zhou et al. 2009b), the size of the national research system (Van Raan 1998), and linguistic features (Csomós 2018; Maisonobe et al. 2016). These facts might suggest that international collaboration patterns vary city to city worldwide, making it impossible to predict cities’ publishing efficiency. However, this question remains to be answered.

In this section, I aim to examine whether cities with high publishing efficiency and cities with low publishing efficiency are characterised by specific international collaboration patterns. Data obtained from the Web of Science database allows us to reveal countries with which the co-authors are affiliated. For example, in the period from 2014 to 2016, 27,322 articles were produced in Ann Arbor, Michigan (United States), from which 765 received enough citations to belong to the top 1% highly cited articles. If we focus on the international collaboration pattern of all articles produced in Ann Arbor between 2014 and 2016, 8.76% of the articles were written with co-authors affiliated with China, 7.23% had co-authors affiliated with Canada, 7.13% had co-authors affiliated with England, 6.78% had co-authors affiliated with Germany, 5.16% had co-authors affiliated with France, and so on. That is, in the case of all articles, the top collaborator with Ann Arbor is China, and the second ranked collaborator is Canada, and so on.

However, if we focus on the international collaboration pattern of the highly cited articles, a different pattern will emerge. Most highly cited articles were written with co-authors affiliated with England (27.32%), with 25.49% from Canada, 23.53% from Germany, 20.26% from France, 17.39% from Italy, and so on. That is, in the case of highly cited articles, the top collaborator of Ann Arbor is England (replacing China as the top collaborator in all articles), and the second ranked collaborator is Canada, and so on.

I examine which countries are the top collaborators (i.e., collaborators ranked 1–5) in the case of all articles and in the case of highly cited articles produced in a given city in the period from 2014 to 2016. Furthermore, I compare the typical international collaboration patterns of the top 100 most efficient cities to that of the bottom 100 least efficient cities. My aim is to reveal whether there is a relationship between cities’ international collaboration patterns and cities’ publishing efficiencies and whether there is a difference between the typical collaboration patterns of the top 100 cities and the bottom 100 cities. When examining cities’ international collaboration patterns, I implemented a geographical constraint. The group of the top 100 cities was divided into two sub-groups (i.e., the most efficient non-US cities and the most efficient US cities), and they were examined separately.

Table 4 shows the countries occupying the top 1–5 positions as collaborators in all articles and their frequency of occurrence in those positions. The top collaborator of the most efficient non-US cities (48 out of the top 100 cities) is the United States, whose frequency of occurrence in the top 1–5 positions is 100% (in the top position in 81.25% of the cases). This means that the United States has a very intense collaboration with every single city belonging to the group of the most efficient non-US cities. Germany is ranked second by collaborating with 87.50% of the most efficient non-US cities in one of the top 1–5 positions. As compared to that of the United States, the frequency of occurrence of Germany in the top position is only 8.33%. In the case of all articles, the top 1–5 collaborators of the most efficient non-US cities are the United States, Germany, England, France, and Italy. As top collaborators, other countries (like the Netherlands, Australia, Spain, etc.) are rather marginal, primarily appearing in the top 4–5 positions.

Table 4

Top collaborators* in the case of all articles.

* In this context, collaborators correspond to countries with which co-authors are affiliated.

In the case of all articles produced in the most efficient US cities (52 out of the top 100 cities), the most frequently occurring countries as collaborators in the top 1–5 positions are Germany, England, China, Canada, and France (Table 4). China, the top collaborator of the most efficient US cities, has surpassed England by almost 2%. The United States has had a traditionally close scientific relationship with Western European countries (especially the United Kingdom) and Canada (Adams 2013), but on the city level, China has recently been occupying a more significant position (Csomós 2018; Tian 2016). Naturally, the top international collaborator of most Chinese cities has been the United States for a long time (He 2009; Wang et al. 2013; Zhang and Guo 1997). If we merge the groups of the most efficient non-US cities and the most efficient US cities into a single group, it turns out that all the co-authors are affiliated with 21 countries occupying one of the top 1–5 positions.

Table 4 illustrates that the international collaboration patterns of the bottom 100 least efficient cities resemble a mixture of the international collaboration patterns of the most efficient non-US cities and US cities. The United States (in the top position in 85% of the cases), Germany, England, France, and China appear in the top 1–5 positions in most cases. However, two facts should be highlighted: 1) As for the international collaboration patterns of the bottom 100 cities, the frequency of occurrence of countries following the United States is much lower than in the case of the most efficient non-US cities. The mean frequency of occurrence of the top 1–5 collaborator countries in articles produced in the most efficient non-US cities is 77.92%. This value is 88.30% in articles produced in the most efficient US cities, but it reaches only 63% in the bottom 100 least efficient cities. 2) The least efficient cities collaborate with a greater number of countries (33) occupying one of the top 1–5 positions than the most efficient cities (21). Many of these countries (e.g., Saudi Arabia, Brazil, Iran, Russia, and South Korea) produce low publishing efficiency; thus, the collaboration has a negative effect on cities’ publishing efficiency (i.e., these collaborations result in a smaller number of articles that receive enough citations to belong to the top 1% highly cited articles).

It is, however, more important to know which countries (more precisely the co-authors affiliated with that country) are the top collaborators of cities (more precisely the authors affiliated with that city) in highly cited articles. According to my hypothesis, countries as the top 1-5 collaborators of cities in highly cited articles differ from those occupying top positions in the total number of articles. The publishing efficiency of cities is heavily influenced by where the top collaborators are in the case of highly cited articles.

Table 5 shows that the collaboration pattern of the most efficient non-US cities in highly cited articles is almost the same as the collaboration pattern that emerged in the total number of articles; however, the relative weight of Germany, France, and England has increased. In the total number of articles, the mean frequency of occurrence of the top 1–5 collaborators was 77.92, while in highly cited articles, this value has increased to 79.17. In highly cited articles produced in the most efficient US cities, the frequency of occurrence of England is 100%, which means that England occupies one of the top 1–5 positions of every single city (in the top position in 57.69% of the cases). Germany has the same frequency of occurrence in highly cited articles than in the total number of articles, but the frequency of occurrence of Canada and especially that of France has significantly increased. China, the third most frequently occurring country in the total number of articles, has vanished from the group of the top collaborators in highly cited articles. This means that, although the total number of articles in US cities shows intense collaboration with China, the collaboration results in only a small number of highly cited articles. In highly cited articles, the mean frequency of occurrence of the most efficient US cities with the top 1–5 collaborators is 81.92%, which is a bit less than in the total number of articles.

* In this context, collaborators correspond to countries with which co-authors are affiliated.

Not surprisingly, in highly cited articles, the bottom 100 least efficient cities have a very intense collaboration with the United States. In 98 cities, the United States occupies one of the top 1–5 positions and is in the top position in 79% of the cases. The frequency of occurrence of countries following the United States is much lower than in the most efficient cities. The mean frequency of occurrence of the top 1–5 collaborators in highly cited papers produced in the least efficient cities is only 63.4%. In the top 1–5 positions, the bottom 100 least efficient cities collaborate with a total of 30 countries, while this value in the top 100 most efficient (non-US and US) cities is 16.

In the case of the highly cited articles, there are fundamental differences between the international collaboration patterns of the most efficient cities and the least efficient cities. Although both groups of cities have roughly the same top collaborators, the least efficient cities collaborate with a much greater number of countries than the most efficient cities. It seems that this difference significantly influences the publishing efficiency of cities.

In conclusion, if co-authors are primarily from countries of the United States, Germany, England, France, Canada, and Italy, which are leading countries in science, articles will have a greater chance to receive enough citations to belong to the top 1% highly cited articles.